User:Adrian Aldrich/Prokaryotic Glutamine Synthetase Pfam Domains Outline

Prokaryotic Glutamine Synthetase Tertiary Structure: PFam domains

Prokaryotic Glutamine Synthetase is a dodecamer, comprised of 12 identical polypeptide chains, organized as a dimer of two disk like hexamers. Each protomer contains 2 Pfam domains, the Beta-grasp domain and the catalytic domain, preceded at the N terminus by short chains(3-13)of resides which link the all protomers together in the dodecamers core.

Beta Grasp domain

The Beta-Grasp Domain is the N-terminal domain, extending from residues 13-94. This domain is responsible for binding ATP, Glutamate, and Ammonia. The domain folds into a bent beta-sheet flanked by two short alpha helices, forming a pocket for the ligands to bind. ATP binds first, activating the site for binding glutamate.

Catalytic domain

The Catalytic Domain is the C-terminal domain, extending from residues 101-382, and forms a melon rind shaped thin beta sheet coated on one side by several alpha helices.

Active site

The dodecamer contains 12  Active sites in total, each formed from the Beta-grasp domain of one protomer and the Catalytic domain of the neighboring protomer. The concave beta sheet of the Catalytic domain( in green ) faces the pocket of the neighboring Beta-grasp domain( in red ), creating a funnel shaped hollow in which binding and catalysis is performed.